1. Field of the Invention
The subject invention relates to stacking methods and apparatus and, more specifically, to methods and apparatus for stacking papers, documents, cards, payment checks, billing stubs, and other sheets of various intermixed lengths, thicknesses and other characteristics.
2. Information Disclosure Statement
The following disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and reasonableness and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necessarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention or which contrast the subject invention or its merits against the background of developments which may be subsequent in time or priority.
U.S. Pat. No. 2,822,171, issued Feb. 4, 1958, for a stacker arrangement, by G. A. Luning, proposes oscillation of card engaging devices between advanced and retracted positions to guide the forward portion of each card into the stacking station in the advanced position and to release the rear portion of each card in succession in the retracted position.
U.S. Pat. No. 2,844,373, issued July 22, 1958, for mail stacking equipment, by F. Van Marle, discloses use of a rotating disc with curved fingers for receiving and depositing sheets in a stack.
U.S. Pat. No. 3,052,467, issued Sept. 4, 1962, for a stacker for intermixed documents of varying size, by F. L. Fertig, discloses combination of a roll and a guide member for providing a constriction through which documents are fed serially and a deflector spring for deflecting the trailing portion of each document.
U.S. Pat. No. 3,148,879, issued Sept. 15, 1964, for stacking apparatus, by H. J. Kistner, discloses a stacking of sheets against a movable wall with the aid of rocking pushers.
U.S. Pat. No. 3,385,598, issued May 28, 1968, for pneumatic filing device, by Jong-Dok Kim, discloses a brake plate having a suction surface for stopping movement of entering sheets, and a mechanical or pneumatic mechanism facilitating the release of each sheet from the brake plate.
U.S. Pat. No. 3,601,265, issued Aug. 24, 1971, for blank stacking, straightening, and delivery apparatus,by A. F. Shields, discloses roller-equipped arms for assisting bottom-fed sheets in their upward travel.
U.S. Pat. No. 3,761,079, issued Sept. 25, 1973, for document feeding mechanism, by L. L. Azure, discloses driving a sheet feed roller through a lost motion clutch.
U.S. Pat. No. 3,805,971, issued Apr. 23, 1974, for stack stabilizer for paper stacking machine, by R. E. Behrens et al, discloses provision of wheels rotatably supported by swingable arms at a stacking station.
U.S. Pat. No. 4,012,034, issued Mar. 15, 1977, for multiple modular sorter system, by J. A. Nelson, discloses actuation of sheet entry gates by rotating cams via cam followers.
U.S. Pat. No. 4,019,730, issued Apr. 26, 1977, for envelope stacking system, by F. J. Staudinger et al, discloses stacking of envelopes against a movable wall by cams projecting through windows at a feed stacker for pushing envelopes out of contact with rollers driving these envelopes into the stacker.
U.S. Pat. No. 4,067,568, issued Jan. 10, 1978, for document feeding and stacking apparatus, by R. Irvine, discloses a rotating structure having rollers attached thereto for transporting documents into a stack.
U.S. Pat. No. 4,068,837, issued Jan. 17, 1978, for paper hold-down device for a collector, by R. A. Lamos, discloses cam-operated hold-down arms for holding down the trailing edge of the stack at an entrance, while the next sheet is fed onto the stack.
U.S. Pat. No. 4,106,766, issued Aug. 15, 1978, for sheet handling and stacking methods and apparatus, by R. Stefansson, discloses stacking of documents against a movable wall with the aid of a thumper which is oscillated in response to power transmission by entering sheets.
U.S. Pat. No. 4,241,909, issued Dec. 30, 1980, for document stacking apparatus, by G. J. Murphy et al, discloses a gravity-bias principle in conjunction with a power drive roller having an elastomeric serrated extended diameter cap, and a roller mechanism, rotatable in a direction counter to that which would normally feed documents through a predetermined path, for retarding the movement of documents and facilitating their stacked arrangement within the stacking cavity. In a commercial version of that type of stacker, a reversely rotating square-shaped elastomeric member is employed in lieu of the document retarding roller mechanism.
In practice, gravity-bias systems are not universally applicable, also, the use of elastomeric serrated roller caps or square-shaped roller members may impose noticeable vibration on the stacking apparatus and entail accelerated wear.
U.S. Pat. No. 4,444,388, issued Apr. 24, 1984, for stacking methods and apparatus, by R. Stefansson, discloses distinct first and second sheet drive rollers which are rocked for a stacking of sheets of various intermixed lengths in a stacking location. While that system has performed excellently, it appears to have an inherent speed limitation beyond which the velocity of the stacking process cannot practically proceed.
Also, many if not practically all of the known stacker systems in practice require extensive controls or mechanisms for controlling the sheet entry gate in addition to any stacking devices. Another factor which has impeded achievement of higher stacking speeds and quality has been an impediment of the sheet entry area at the stacker by the stacking means themselves.